In a typical elevator group comprising a plurality of elevators, elevator calls are allocated to individual elevators by the elevator group control unit by using an allocation algorithm.
The allocation algorithm tries to optimize the operation of the elevator system by minimizing certain cost factors. An example of an allocation algorithm is disclosed in published patent application WO 01/65231 A2.
In certain situations it may happen that two or more elevators would be equally well or almost equally well in view of the allocation algorithm.
In such cases, the elevator group control unit normally selects the elevator that is used to serve the call by using a straightforward method. Normally, the elevator with the smallest order number in the elevator group is selected. In an exemplary situation, if elevators B and C are waiting in the 2nd floor and the passenger gives a call in the 1st floor, the elevator B will always be selected, even though elevator C would be as good or almost as good as the elevator B.
In modern elevator groups, one or more elevators may be returned to the floor in which peak traffic time passengers are waiting or are supposed to be waiting. Generally, such peak traffic is experienced in office buildings in the morning (people coming to work) in the floor with entrance(s) to the building, and during lunch break in the floor(s) with restaurant facilities. In certain mode(s) of operation, therefore, the allocation algorithm in the elevator group control unit selects the elevator with the smallest order number in the elevator group.
Such operation mode may be activated also outside peak traffic times.